


You Got to Be Kitten Me

by JadedFrisk



Category: Undertale (Video Game)
Genre: F/M, Smut, Underfell
Language: English
Status: Completed
Published: 2019-02-14
Updated: 2019-02-14
Packaged: 2019-10-28 00:24:58
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,124
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17777057
Author URL: https://archiveofourown.org/users/JadedFrisk/pseuds/JadedFrisk
Summary: This is for my friend on Discord, Venya. You can call it a Valentine's Day Gift. Love ya Girl! (Beta'd by Lexi as well)Frisk wanted to surprise Sans this Valentine's Day, but couldn't help trying it out first...





	You Got to Be Kitten Me

**Author's Note:**

> Purely a sex scene. If you don't enjoy or wish to read such, turn back now. If you do, well enjoy!

Sans grumbled to himself as he made his way home from Grillby’s. Not sure if he wanted to go back, the skeleton played with the spiked collar around his neck. The item had been given to him as a source of humiliation at the hands of Papyrus, but ever since Frisk had taken a liking to it, one could say he never planned to remove it. Thinking more of her, Sans had recently noticed that the young woman had begun to act strangely around him. Anytime the skeleton was in the room or brought up her strange behavior, she’d seemingly need to be elsewhere. It was really starting to piss him off. They had been dating about a year now, wasn’t he privy to this thing that she was up to? Frisk had to know how much he hated surprises by now, right? Snow fell, landing on the ridge above his nasal cavity, causing Snowdin to live up to its namesake. Going cross-eyed to stare at the offending flake, Sans failed to realize he was standing in front of the house until Papyrus snapped at him.

“DO YOU PLAN TO STAND IN MY WAY ALL DAY?!” The tall skeleton tapped his phalanges against his elbow-length red gloves.

‘Well shit. He seems to be in a mood…’ Shifting out of the way, he replied, “Sorry Boss, wasn’t paying attention.”

“OBVIOUSLY.” Irritation laced Papyrus’ voice as he walked out from the doorway. “THE GREAT AND TERRIBLE PAPYRUS HAS NIGHT TRAINING TO ATTEND TO. I EXPECT TO COME HOME TO THE WHOLE HOUSE SO DO NOT DESTROY IT WHILE I AM GONE. UNDERSTOOD?”

The shorter skeleton just nodded. Seeming satisfied with the reply, Papyrus began his trip to wherever it was that the training would be held at. Sans scratched his skull, completely confused. Then again, Frisk was now home alone, or so she would currently believe. His signature smirk widened as a plan formed in his mind. A prank to end all pranks was about to begin.

~-o0o-~

Frisk stared at the contents of the box in front of her. Contemplating why she had bought all this, the young woman began unpacking. She pulled out a pair of red, fuzzy cat ears with a chuckle. They were adorable, and in Sans’ favorite color to boot. Blushing deeply, Frisk raised the next item out. A crimson-furred cat tail attached to a stainless steel butt plug rested in her hands. Quickly placing it next to the ears, she reached in once more. This time, a red leather collar came out, tiny silver skulls wrapping around it while a silver bell rested at the center. The softness of the leather and the equally gentle chime of the bell made the young woman smile. Adding it to the other intimates, she reached yet again into the box’s depths, pulling out a red and black feather. Such an innocent-looking long plume, for rather naughty purposes. Next drawn from within the chest was a long silver chain, ending in a black leather handle. Her new leash, replacing the one that Papyrus had broken while saying that she wasn’t a pet and needed no such thing. If he had known what she had planned, the tall skeleton would never look at her the same way. Grabbing the pair of fuzzy handcuffs and gazing at them, she hoped that Sans couldn’t get out of them. They were magic-blocking, after all. Placing the handcuffs down, she withdrew a bullet vibrator next, followed by a translucent red dildo. It had reminded her of his cock, a must-have for when her boyfriend wasn’t around. Now able to appraise all of the contents of the box at once, Frisk smirked at her haul. 

Removing her clothing, the young woman stood there naked before the toys. She reached down to retrieve the butt plug first. Walking to her bedside table, she opened the singular drawer, rustling about until she retrieved her lube. Applying the solution evenly around the toy, she put the metal piece between her cheeks. The cold bite of the steel made her shiver more than its slow, careful insertion. She let out a low grunt as the plug finished sliding all the way in. Red fur peeked from between her legs, tickling her whenever she moved. It felt odd, but certainly not bad. The ears were the next thing to be put on, purrly for cosmetics. Next wrapping the collar around her neck, she noted how the hide felt cold yet soft against the skin beneath. Frisk then locked the leash onto the clasp of the collar. Before heading back to her bed, the woman picked up two more items from her trove and quickly cleaned them with some toy wash she conveniently had placed nearby. Hopping on the mattress, she got down on all fours, reaching for the vibrator. She turned it on, relishing in the vibrations already just between her fingers. Lowering it down along the length of her body, she circled it around her nipples, causing them to harden and adding to the pleasure. Once happy with the state of affairs of her breasts, the young woman continued down her body. The oscillations against her flat stomach only caused her to giggle, as she was highly ticklish, but despite that, she persevered on her journey to the ‘promised land’. Frisk jumped slightly as the toy reached her clit, the bundle of nerves instantly sending red-hot pleasure through her whole body. The entrance below twitched and began to get moistened with each pass of the vibrator. Believing herself to be sufficiently ready, she groped nearby to grasp the dildo next. It wasn’t as big as Sans, but then again, very little really was. She angled the thick, red dong against her womanhood, ready for its girth to fill her. Sliding it in, Frisk muffled a moan of pleasure with the bed beneath her. The vibrator lay unused in one of her hands until she was sure that the whole length of the other toy was within her. Once again, she started her assault on her clit with the pulsating bullet. Her moans got louder and her need climbed higher. At that moment she wanted nothing more than her boyfriend’s warm tongue on her nipples as she pleasured herself to thoughts of him. Frisk was so lost in her fantasies that she had failed to realize she wasn’t alone; that is until a very real, present appendage actually did run across her nipples, and warmly sucked one of them into a waiting mouth.

~-o0o-~

Proud of himself, Sans looked at his handy work. The prank was all set up and ready for its victim. He smirked as he thought about how she’d react to it when he heard a loud cry coming from the bedroom that could only have belonged to Frisk. It had been hers since she arrived there. Papyrus had thought it would only be right for her to have a room instead of sleeping on the couch all the time. Making his way up the stairs, the skeleton listened carefully, trying to make out what was going on. Another cry came from her room, pushing him to teleport in since he believed her to be in danger. He wasn’t prepared for what he saw.

Frisk was on her bed, the plush pink comforter messy from movement, with a dildo in her pussy and a fuzzy tail sticking out of her ass. The position combined with the tail, ears and leashed collar made her look like a cat in heat. To top it all off, it was in his favorite color: red. A new and somehow more devious smirk crept its way across his face as he silently got closer to the ‘playful kitten’. It wasn’t too surprising to him that he went unnoticed, but that was fine by him. Letting his tongue come out to play, he ran it across her left nipple, which he sucked into his mouth. Frisk let out a yelp before her wide eyes found who was there. Green irises met red lights as he, much like a baby, suckled her breast. Sans reached up and fondled the other, neglected nipple. The woman let out a moan, letting the vibrator drop onto the bed in her pleasure. He chuckled, sending a ripple of gratification through her breast and causing her to moan more. Suddenly, the skeleton let go of her nipples and looked her over.

“So, Kitten, mind explaining this?”

The woman looked slightly embarrassed, avoiding eye contact with her boyfriend. “I…I got some new…toys. Wanted to try them out before we used them...together...” She somehow managed to string the words together through her pants and soft moans.

“Oh. Is my Kitten in heat from these? Does she want me to help her with it?” Sans chuckled as he continued coyly. “I don’t mind helping my pet through this.”

She shivered upon hearing his offer. “I’ve been a bad kitty, Sans. I started without you, pleasuring myself only to thoughts of you, with toys that aren’t as filling as your…” Frisk shook her rear, causing the tail to swish as she murmured “...cock.”

If he hadn’t been hard before, that certainly had done him in. “Well if Kitten wants it she’ll have to move and let me into her territory.”

Moving backward along the mattress, Frisk let Sans sit next to her on her bed. A tent in his shorts glowed bright red as his raging cock strained against the fabric that contained it. She tentatively reached for the waistband of his shorts, tugging them down to free the ‘monster’ within them. It instantly sprang out, seemingly all-too-happy to be freed from its prison. Frisk licked her lips as she moved her head closer, feeling the heat radiating off the magical member. The skeleton just sat there, watching her, letting the woman do what it was that she wanted. Using her hand to steady his member, she opened her mouth to engulf the proudly standing head. Sans hissed in pleasure as her head slowly lowered over his girth. He had forgotten how good she was at giving head. Teeth gently scraped the underside of his cock as she bobbed up and down, as though to some unheard musical rhythm. The skeleton began to pant, his hand clacking out to push her head down and speed up her pace. Frisk glanced up at her boyfriend, a smirk forming on her face as she sucked harder. 

“Gods Frisk…” He held her head down as he came in her mouth, red cum spilling from the corner of her lips as overflow. She still swallowed what she could, watching his face the whole time. Once his eye-lights came back, Sans looked at her, muttering “You spoil me so.” Wiping away the cum on her chin, he bent down and kissed her hard, tasting himself in her mouth. She kissed him back with matching need; the need for him to be inside of her.

Sans got up, removing all of his remaining clothing. The woman playfully backed up, pretending to be afraid of him, which made him even harder than before. He stalked her, his member bobbing as he walked back to her, more than ready to pound her. Pinning her down when she tried to ‘get away’, the skeleton maneuvered himself so his cock prodded her entrance, never truly entering her as the dildo still occupied it. She whimpered, shifting her body to try and push onto him.

“Oh no, bad Kitten.” He pushed her body against the comforter-covered mattress swiftly. “I’ll give you the treat when you’ve earned it.”

Rubbing her breasts roughly with his hands, he used his blue magic to hold her in place. Moans and cries gave him all the encouragement he needed to continue. He gently ran his finger bones over her stomach, so as to not cause her to laugh by tickling her on the journey to her clit. As he finally reached the bundle of nerves, he pinched it firmly, causing Frisk to arch up against his magic as flames of pleasure erupted in her. Sans smirked at this reaction to his ministrations, continuing them at a steady pace.

“Please, Sans…” Her voice trailed off.

“Please what?” he replied to her.

“Fuck me…”

Blunt and to the point; he could appreciate that, but still wasn’t about to just do it. Grabbing the red dildo, he pulled it almost all the way out before slamming it back into her. The woman let out a loud cry, only spurring him on. Pushing and pulling, he fucked her hard with the imposter cock. Sans knew full well that while this was a useful tool, it would never compare to his own member. Ascertaining that she was on the edge of her orgasm, the skeleton stopped and removed the dildo unceremoniously, throwing it haphazardly onto the floor. Frisk whined and tried to move back so he would fill her, but she was stopped again. It was truly torturous; she was needy, didn’t he know this? A hand grazed across her ass, grabbing the base of the butt plug tail. She cried out and, taking the hint, ceased movement enough to give him time to chain her to the bed with the leash. Climbing off of the mattress, Sans grabbed the fuzzy handcuffs before coming back to the bed.

“Now, you’ve been a very bad Kitten. I need to restrain you. Resist and I’ll punish you more.” Taking her hands, he cuffed them to the metal headboard. He fell back a bit, cock standing proudly in front of her while he admired the view. Oh, how much Frisk wanted that thick length inside her, but trying anything would only delay it. “Now…should I breed this little Kitten?”

Frisk nodded frantically in response. “Kitten wants it so badly…” Her reply ended in a whimpering moan.

“Oh but she’s been bad lately. Having fun all by herself and not inviting others to join…” Sans grinned wickedly as she became more and more desperate. “Must not want my cock if a toy would suffice…”

She let out another desirous whimper. “Please? I’ll be good. I want you inside me so bad Sans. Mount me, ride me hard!” Trying to lift her ass higher, the woman attempted to coax him to take her.

“I suppose I could let this slide for now. IF she promises to invite me next time to her little play dates.”

Frisk nodded frenziedly, nearly gushing the words “I promise.”

“Good.” His weight caused her to shift unsteadily as her balance was thrown off. The lack of ability to use her arms to steady herself really made it difficult to stay stable. She could feel his smooth leg bones cradling her thighs as he mounted her like a lion about to breed his lioness. His hot member twitched, hitting her stomach as his body gently laid on hers. “You’re so fucking beautiful Kitten. I love fucking you till you can’t move anymore.”

“Please Sans, oh gods, please mate me hard.”

He chortled, drifting his hips upward as he did. “Since you said please.”

The warmth of his cock hit her entrance as he pushed its head into her at a painfully slow rate. Sans knew she wanted it fast and hard, her need so apparent on her face, but he wanted to torment her at least a little more. It was agonizing for her, and she tried to buck against him but the restraints stopped her. He was in control of this, as he always was. Eventually, the head of his cock disappeared into her, his pace unchanged until it was up to the hilt inside. The skeleton relished the feel of his girlfriend, how tightly she gripped his twitching member. It was a paradise to him, but even he had limits. Pulling back, he slammed his cock back into her vigorously, shaking the bed with the force. Frisk unleashed a scream of pleasure as he began to repeatedly pull out only to collide with her again. This was what she had wanted; hard sex with that massive cock of his. Her climax was building again as he fucked her hard, the bed squeaking with each impact. Moans and grunts escaped him as he hammered her, his own orgasm coming to a head. A few more thrusts and climaxes were achieved, Sans filling her thoroughly with his sticky, red seed. A flashing thought reminded him that he had forgotten any contraceptive in the heat of the moment, but it was too late now. Whatever came of this, if anything did, they’d face it together. The skeleton was never letting this woman get away from him. Pulling out, he marveled at her panting form. An idea struck him. He undid the cuffs and swiftly flipped her onto her back. Now splayed out on the mattress, Frisk was still coming down from her post-orgasm high.

“Hope you got enough energy for round two Kitten.”

Her eyes widened at his words. “Round two?”

His smirk said it all: Sans planned to take her again. Frisk let out a mew as he lifted her legs up so he could get under her slightly. The skeleton rested her ankles on his shoulders, slipping his cock into her still-slick pussy. Yet extremely sensitive from their first lovemaking, the woman let out a raspy cry of pleasure. He took her again, fast and hard, his need overriding all other thought. Sans wanted this, no NEEDED this. His body jerked forward and back in a dance as old as the world itself. They would go on to have sex two more times after this. Each time, Sans would cum inside her without anything to stop his seed from doing what it does best. After all, what being thinks of such when in heat?

~-o0o-~

Months had passed since that toy-infused sex fest had happened. Sans sat on a fading green couch, Frisk sitting next to him. Not long after their fevered evening, the woman had freed all the monsters from the Underground, allowing them to start new lives on the surface. It was hard to adjust to, but they would make it. His hand gently rested on her swollen belly, a genuine smile plastering his face.

“What do you think it will be Sans?” his mate inquired softly.

“Not sure Kitten, but I’m sure it will have your determination.” He chuckled.

“And your puns.” She smiled at him.

“Though I have to say…”

“Hm?” Frisk looked up at him curiously.

“You’re awfully big to be only one..”

The thought had never occurred to her. What if there was more than one? Oh, dear gods...

**Author's Note:**

> Hope you all enjoyed it. I really hope Venya enjoyed it as much as I had fun writing it. Happy Valentine's Day!


End file.
